Technician A says when the Brake warning light is illuminated, there is a difference in pressure between the two brake hydraulic circuits. Technician B says the Brake warning light is illuminated when the fluid level in the master cylinder reservoir is low. Who is correct?

The both technician , both technician A and technician B.

Explanation:

If the brake warning light comes on when you apply the brakes, or is on continuously, it means that hydraulic pressure has been lost in one side of the brake system or that the fluid level in the master cylinder is dangerously low (due to a leak somewhere in the brake system).

Low Brake Fluid: Your Parking Brake light is a multifunction device, and is designed to illuminate if the fluid level in the reservoir drops below a certain point. You may notice the light turning on or off when going around turns as the fluid level changes. ... It can also turn on the Parking Brake light in your dash